frost flower

It cooled down very much on the 23rd.
This coldness made beautiful frost flower.
Japan Meteorological Agency said that it was -15.3°c, our thermometer pointed at -18°c.
The day before 23rd, a stream was flowing.
But now it was frozen.
Frost flower needs four conditions.
1, Temperature is -15°c.
2, No wind
3, thin ice
4, no snow
We have never seen same pattern of frost flower.
And it is hard to see mysterious scene.